1. Field of the Invention
The present invention relates to a test strip, a detecting device, and a detecting method, and more particularly, to a test strip, a detecting device, and a detecting method used to obtain a flow time of a specimen and use the flow time to correct a concentration of the analyte of the specimen.
2. Description of the Related Art
Electrochemical bio-sensors have been widely adopted to find out the concentration of the analyte in a liquid specimen, such as blood or urine. There are many kinds of electrochemical bio-sensors, such as blood glucose sensors, cholesterol sensors, uric acid biosensors, and lactic acid biosensors. In particular, blood glucose sensors have become indispensable for diabetics. Generally, a blood glucose sensor is formed in a strip shape and comprises at least two electrodes such as a working electrode and a reference electrode for receiving electrical signals proportional to the concentration of the blood glucose in a blood sample and transmitting the electrical signals to a blood glucose meter to indicate the blood glucose level.
On the other hand, whole blood viscosity test can provide reliable reference to the diagnosis and treatment of pre- or post-thrombus in many research and clinical experiments. Numerous diseases such as hypertension, cardiopathy, coronary artery heart disease (CAHD), myocardial infarction, diabetic, malignant tumor and chronic hepatitis are highly related to blood viscosity. Blood viscosity could be affected by the size, shape and hematocrit of red blood cells, which are the major part of the blood; although white blood cells and hematoblasts also could affect the blood viscosity; therefore, hematocrit (HCT) is the key factor in deciding the blood viscosity. Furthermore, when the blood viscosity increases, there will be more resistance in the blood, making it difficult to supply blood to the heart, brain, liver and kidney. As less blood is supplied, the symptoms could become worse; therefore, the blood viscosity has become an important index in monitoring the disease.
In order to measure the blood viscosity, there are many types of viscometer, such as capillary viscometer, cone and plate viscometer, coaxial cylinder viscometer, and pressure sensing viscometer, in which capillary viscometer is the most popular type. In a capillary viscometer, when parameters such volume, pressure difference, capillary diameter, and capillary length are constant, then the viscosity of the fluid is proportional to the time required to flow through the capillary; therefore, when the fluid is filled in the capillary, the viscosity of the fluid is obtained by using Poiseuiller's principle. However, there are some restrictions in using the capillary viscometer, for example, the capillary have to be straight, long and round in its cross section, the length to diameter ratio of the capillary usually needs to be more than 200, and the diameter of the capillary is larger or equal to 1 mm, and so on. Besides, the capillary viscometer has large equipment size, it needs a lot of sample volume to process and tends to require long reaction time; therefore, it is not easy to clean the capillary viscometers, and it is not convenient to carry the capillary viscometer with the patient to detect the blood viscosity in real time. When it is necessary to obtain blood viscosity data from a group of people, it takes a great amount of time in detecting blood viscosity from each one of them and it requires getting enough specimens from them; therefore, it is inefficient and also not cost-effective.
Apart from the method for measuring blood viscosity as depicted above, US patent application US2007/0251836A1 disclosed an electrochemical sensor and method for analyzing a liquid sample, in which the electrochemical sensor comprises a channel for delivering the liquid sample; and a first conducting portion and a second conducting portion separated and exposed in the channel; wherein the first conducting portion generates a first pulse signal when it is contacted by the liquid sample, and the second conducting portion generates a second pulse signal when it is contacted by the liquid sample. The electrochemical sensor obtains viscosity of the liquid sample according to a time difference between the first and second pulse signals. Generally an electrochemical sensor provides a voltage no higher than 0.5V to save power and to avoid triggering unnecessary reactions; however, the signal could be very weak and unstable between the liquid sample such as blood and the electrodes, it could be covered by background noises and is difficult to be detected. Furthermore, the electrochemical sensor can be used to correct the concentration of blood glucose, to do so, the electrochemical sensor has to include an enzyme in its channel. In order to save space for test strip, the electrode set for detecting the blood glucose concentration is disposed between the first conducting portion and the second conducting portion, when the liquid sample flows into the channel, the electrode set begins detection at the same time. In other words, the reaction of the enzyme and the detection of the flow time happen in the same channel and could easily interfere with each other; besides, the enzyme disposed on the electrode set also comprises mixtures such as polymeric binders, stabilizers, buffers, surfactants, which could cause the fluidity of the liquid sample to change and often lead to differences in flow time detection. Besides, since the enzyme is provided for reacting with the analyte of the liquid sample to detect the flow time, the flow time signal will not be obtained until the blood samples reacted with the enzyme, otherwise a weak signal or a delayed signal will be detected. Therefore, the prior art technique cannot provide stable detection results and often fails to reproduce itself.
U.S. Pat. No. 7,258,769 uses enzymes to react with blood samples to detect the fluidity of blood and the concentration of blood glucose, when enzymes are added to the test strip, the following reactions would occur:Glucose+Gox-FAD→Gluconic acid+Gox-FADH2 Gox-FADH2+Mox→Gox-FAD+Mred
In the reaction formula, Gox stands for Glucose Oxidase, which reacts with blood glucose to transform into a reduced state, and then the reduced Gox reacts with electron transfer mediators to let the electron transfer mediators transform into a reduced state. Afterwards, the reduced electron transfer mediators would spread to the surface of the electrode and are oxidized by the anode, thereby generating a current for obtaining the concentration of blood glucose. When performing the fluidity detection, it is necessary to wait for blood glucose to react with enzymes to generate a detectable signal, however, by that time the blood may has already flowed through the electrode, so the generated signal does not reflect the real fluidity. Therefore, enzymes disposed in the channel can be used for detecting blood glucose but not for determining the flow time. Since the detection signal can only be generated after the blood sample reacts with enzymes, there will be a time difference between the actual fluidity and the measured fluidity.
U.S. Pat. No. 8,080,153 proposed a method and a system of determining a hematocrit-corrected concentration value of an analyte in a sample. The method comprising: using three reference electrodes with a working electrode in a sampling area to determine a fill time of the sample on the test strip, using enzymes in the sampling area to detect a concentration of the analyte, and then calculating a hematocrit-corrected concentration of the analyte using an empirical formula with the fill time. FIGS. 1A and 1B show FIGS. 4 and 5 of the patent, respectively. As shown in FIG. 1A of this patent, it is clear that when the hematocrit increases, the fill time values tend to scatter, which implies that the patent does not do well in reproducing itself. As show in FIG. 1B, when the hematocrit increases, the concentration of blood glucose reduces, and the number of red blood cells increases. Red blood cells tend to affect the reaction between electron transfer mediators and blood glucose; besides, blood plasma could affect the diffusion of electron transfer mediators as well, so the concentration of blood glucose could be lower than expected. In FIG. 1A, when the fill time is 0.8, it is difficult to determine the hematocrit (which could be 55% or 65%), which in turn would affect the value used to compensate the blood glucose; in other words, this patent could obtain an undesired corrected concentration of the analyte. Generally a male adult has a hematocrit value of between 39 to 50%, while a female adult could has a hematocrit value of between 36 to 45%. A diabetic often suffers from other complications such as high blood pressure, anemia or other heart disease, so the hematocrit of the diabetic could easily become abnormal. When the hematocrit exceeds the normal range, the concentration of the blood glucose could have apparent deviations and needs to be corrected to avoid erroneous judgement and even putting life in danger.
Since the prior art techniques cannot precisely obtain blood viscosity within a short amount of measurement time. The present invention discloses a test strip, a detecting device, and a detecting method to solve the problems present in the prior art techniques.